The main objective of Project 11, Tools for Tissue Engineering Tooth Structure, is to make a mouse model applicable to tissue engineering of dental hard tissues. We seek to understand how the structure and properties of mouse dentin are related to human dentin. Second, we must understand how biological factors acting in the in vivo model are related to actions in vitro, as tissue engineering strategies often require tissue formation in culture and subsequent implantation. These premises led to our objectives aimed at developing tissue engineering tools for dental hard tissues. We will determine: 1) if the mouse model is relevant to human dental hard tissues; and 2) if members of the TGF-B superfamily of growth factors can provide insight into dental tissue mineralization processes. The understanding of this mineralization process is prerequisite to developing tissue engineering approaches in restorative dentistry. In order to understand how TGF-B affects relevant cellular activity, incisors and molars of transgenic mouse models with altered production of or response to, TGF-B in odontoblasts and cementoblasts, as well as cell cultures will be used. Initially, we will study two mouse lines, one that expresses a dominant negative form of the type II TGF-B receptor (IIRDN mice), and the other that over expresses TGF-B2, both driven by the osteocalcin promotor. Based on previous findings in the bones of these mice and our preliminary studies of their teeth, it is expected that the tooth phenotype of TGF-B2 mice to be inverse of that found in IIRDN mice. The specific aims are: 1) To characterize the structural, biomechanical, and biochemical properties of mouse teeth to validate their use as models of human teeth; 2) To determine the effect of TGF-B on matrix metabolism and mineralized tissue architecture by using transgenic mice with altered production of, or response to, TGF-B; 3) To determine the role of TGF-B in tissue repair by examining reparative dentin formation in IIRDN, and TGF-B2 transgenic mice; 4) To determine the effects of TGF-B1 and B2 on proliferation and differentiation of pulp stem cells in vitro. These studies will help determine how TGF-B affects normal dentin/cementum formation through odontoblast/cementoblast responsiveness, if cementum turnover is similar to that of bone, and how the effects of TGF-B on matrix production are related to the physical properties of mineralized tissues, as well as provide insight into effects of these growth factors in vivo and in vitro.